1. Field of the Invention
The present invention relates to an electronic instrument having a magnetic sensor, particularly to an electronic azimuth indicator including a part having magnetic susceptibility that affects a magnetic sensor, or to a various kinds of electronic instruments provided with such an electronic azimuth indicator.
2. Description of the Prior Art
As an example of such an electronic instrument that has been conventionally used, there is a wristwatch provided with an electronic azimuth indicator. Such a wristwatch with an electronic azimuth indicator has a problem that, when a magnetic sensor is arranged in the vicinity of a part that is susceptible to magnetization or a part assuming magnetism, accurate detection of a direction is difficult because such a part adversely affect the magnetic sensor.
To describe it more concretely, geomagnetism can be generally regarded as an even magnetic field. When a spherical magnetic body is arranged in such an even magnetic field, the magnetic field is distorted as shown in FIG. 14. FIG. 14 shows a state of the magnetic field in which a spherical magnetic body is arranged in an even magnetic field. As can be seen from the figure, the direction of the magnetic field is deflected to the direction of a spherical magnetic body 19 as shown by a magnetic field 9a in the vicinity of the spherical magnetic body 19. Such a phenomenon is observed when an article assuming magnetism (a magnetic body) is placed within the magnetic field.
In addition, an electronic instrument such as a wristwatch with an electronic azimuth indicator uses a magnetic body such as a battery and a capacitor, and particularly there are a lot of button batteries that use 304 stainless steel processed to have a circular shape. Although it is generally considered that such 304 stainless steel does not have magnetism, when the stainless steel elongates due to die cutting or bending, magnetism may occur in the direction of the elongation.
For example, as shown in FIG. 15, if the entire outer configuration of the circular stainless steel is processed to elongate in the circumference direction, the elongation occurs from the inside to the outside with respect to the outer configuration as shown by arrows. Magnetism is observed with the direction of the elongation as an axis.
Therefore, when it is necessary to arrange a magnetic sensor in the vicinity of a magnetic body or a button battery, there is a possibility that detection of magnetic field components is adversely affected due to the above -mentioned effects.
As prior art for solving this problem, there is the invention described in the Japanese Patent Application Laid-open No. Hei 6-309869. In this prior art, a distance between various kinds of electronic parts and a magnetic sensor that is sufficient to eliminate influence of the electronic parts is studied in detail, and the position of the magnetic sensor is determined based on the study. That is, the magnetic sensor is arranged as far as possible from an electronic part that is susceptible to magnetization to make the influence of the electronic part to the magnetic sensor minimum.